Hard-hitting political ads against President Barack Obama, U.S. Sen. Bill Nelson and U.S. Rep. Allen West are popping up across Florida in a scramble to define the message of the 2012 elections, still 16 months away.

But the radio and TV attacks — which focus on jobs, Medicare and the federal debt — are not paid for by the candidates' opponents or the Democratic and Republican parties.

They are launched by so-called independent expenditure groups that are forming at remarkable speed, raising tens of millions of dollars and fundamentally altering political campaigns.

And you may never know who those contributors are — or their motivations — due to a provision of law that is increasingly exploited by Republican-aligned groups and, now, Democrats.

Through they decried the practice last election — "A problem for democracy," Obama said in October — Democrats are racing to create their own groups, trying to prevent a further erosion of power in Washington.

If the 2010 midterm elections seemed a busy time, brace yourself.

"We're going to see a tidal wave of cash like we've never seen before," said Bill Allison, editorial director of the pro-transparency Sunlight Foundation in Washington, which tracks the groups. "You probably won't be able to turn on SpongeBob SquarePants without seeing political advertising."

Florida is getting early attention — along with Colorado, North Carolina and Virginia — because it is a critical battleground for the presidency and control of Congress. The outside groups are jumping in early, hoping to set the tone and define their opponents.

"For the president, Florida is a pressure point," said Jonathan Collegio, spokesman for the conservative Crossroads GPS, which is spending $20 million in July and August in various states and plans to raise $120 million through the elections.

On Monday, Crossroads launched a Spanish-language ad in Tampa, Miami and Orlando attacking Obama and congressional Democrats' economic record. (The Democratic National Committee scrambled to produce its own ad, which began airing Friday.)

In June, Crossroads spent $700,000 in Florida on an anti-Obama ad, based on criticism of the economic stimulus. The mocking ad was titled "Shovel Ready."

That led to a retort from the pro-Obama group Priorities USA Action, begun in April by a former Obama aide. "The Republicans have opposed economic reforms at every turn," a narrator said in the ad, which ran in five states at a cost of $750,000.

Crossroads, which is affiliated with well-known Republican operative Karl Rove, spent more than $530,000 on a TV ad attacking Democratic Sen. Nelson for his votes for the health care law and $787 billion economic stimulus.

Meanwhile, a pro-Democratic group, House Majority PAC, ran a radio ad ripping West, the controversial South Florida Republican congressman, for supporting a plan that would overhaul Medicare.

"We're starting as soon as possible," said Ryan Rudominer, a spokesman for the group, which formed in April.

The group has targeted 14 congressional Republicans across the country in two ad buys that were six figures each. And earlier this year, it spent $400,000 in a heated special election in New York that turned in Democrats' favor after the GOP passed the Medicare plan.

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The independent expenditure groups, and scores more like them, are known as Super PACs because they can raise unlimited amounts of corporate and union money, as well as from individuals.

They are blossoming — 114 since 2010, including 46 this year alone — due to recent changes in campaign finance law.

At the heart is Citizens United vs. Federal Election Commission, a landmark U.S. Supreme Court decision in January 2010 that lifted century-old limitations on corporate money in federal elections by allowing businesses and labor unions to spend as much as they want — directly in favor of or against candidates, so long as the action is independent of the candidate and campaign.

Some, like House Majority PAC, disclose donors. But others are organized under section 501(c)4 of the tax code, which does not require disclosures.

Traditional political action committees, candidate campaigns and political parties disclose donors, allowing voters (and journalists and government watchdogs) to see who is backing a candidate and make connections to what issues politicians push and how they vote.

“Citizens United is the worst, the most dangerous decision in the country since Dred Scott," U.S. Sen. John Kerry, D-Mass., said last week, referring to the 1857 ruling that blacks were not citizens.

Conservative groups in 2010 rushed to form Super PACs and outspent Democratic-aligned ones by tens of millions. Crossroads GPS and affiliate American Crossroads, which discloses donors, raised $71 million in 2010.

The ads focused on health care and federal spending and helped Republicans take over control of the U.S. House and close the gap in the Democrat-controlled Senate.

Democrats were outraged.

"If you're in a battleground state right now, you are being bombarded with negative ads every single day and nobody knows who's paying for these ads," Obama complained during an election forum in October. "They've got these names like 'Americans for Prosperity,' or 'Moms for Motherhood.' Actually, that last one I made up," he laughed. "They've got these innocuous-sounding names and we don't know where this money's coming from. I think that is a problem for democracy."

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But Obama's allies are racing to form their own third-party groups, saying they have no choice but to fight back.

Priorities USA Action, the group that ran the pro-Obama ad in Florida, was set up by Bill Burton, a former Obama aide. The group does not disclose donors.

"We may not like the rules," Burton said when asked about the disconnect from 2010. "But to paraphrase Donald Rumsfeld, 'You go to war with the rules you have, not the rules you wish you had.' "

Collegio, the Crossroads spokesman, called the move "brazen hypocrisy."

"If they really believe it was a threat to democracy, I don't think you'd get involved in one of these groups," he said.

He defended the Crossroads GPS practice of nondisclosure, saying high-profile donors who have been named, such as Bob Perry, a Texas home builder who helped fund the Swift Boat Veterans for Truth attacks derailing Kerry's 2004 presidential run, have faced bruising criticism. Perry last year pumped $7 million into American Crossroads.